Research On Flowing Features Of Slurry In Chemical Mechanical Polishing

Chemical mechanical polishing(CMP)is a processing method with unique advances.It has been widely used in Microelectronic field and optical machining field.In CMP,slurry plays the role of transporting chemicals reaction material,removing machining debris.The flow process of slurry can deliver chemicals and abrasive to the surface of the polishing pad,take away the heat generated by friction and processing products,maintain a stable environment At the same time,slurry between the workpiece and polishing pad can establish lubrication film bearing capacity in flow,improving the contact state with the polishing pad.In order to understand the chemical mechanical slurry flow rules and effects of polishing pad on surface morphology of slurry flow,optimize the surface morphology of the polishing pad to control the flow of slurry,this paper carried out the following research:1.Analysis of the flow state of the slurry on the surface of a flat polishing pad.Using the fluid mechanics equations and finite element analysis method to analyze the state of slurry with no viscous.The results show that the slurry has an accelerating movement trend from the inside to putside.as well as increasing the wetted perimeter length,with the height significantly decreased.The flow uniformity is poor.The simulation results are verified using particle image velocimetry experiments.2.Combined with the finite element simulation of multiphase flow model and the particle image velocimetry experiment,the flow characteristics of the slurry on the polishing pad with grooves were explored.The flow of slurry in the groove is affected by blocking effect,and slurry flow energy losses significantly.Compared to the flat polishing pad,the pad surface having a groove has a higher thickness of the liquid film.And it's not easy to cause the debris deposition,which is conducive to the efficient discharge of debris.The velocity change from inside to outside of the radial has been improved to some extent.In this paper,the flow states of the polishing pad with different groove shapes are compared and discussed.The results show that the uniformity of the slurry flow is the best when the grid is hexagonal.3.Groove design of polishing pad.On the basis of the theory of the energy loss of the slurry,the groove of the polishing pad is optimized.The optimization involves the groove width to depth ratio,the groove size and the groove direction along the surface of the polishing pad.Analysis to the slurry in the groove using the finite element simulation was carried out.Results show that the flow velocity and film thickness is uniform.The experimental results also show that the groove radial velocity is uniform,which achieved the expected optimization effect.